Jack Berndhard Hermansson (born June 10, 1988) is a Swedish professional mixed martial artist, currently living in and fighting out of Norway. He competes in the Middleweight division of the Ultimate Fighting Championship (UFC). As of 8/30/2022, he is #8 in the UFC middleweight rankings.

Hermansson was born and raised in Uddevalla, Sweden, growing up alongside six siblings. Hermansson began training in Greco-Roman wrestling at age nine. At eighteen Hermansson began training in Muay Thai and MMA. A move to Norway to work as a substitute teacher would put Hermansson in touch with members of Team Hellboy (later Frontline Academy), run by Norwegian MMA pioneer Joachim "Hellboy" Hansen. As Hermansson got older and worked various odd jobs at a pet store and a bar he decided to take his MMA training more seriously and to pursue a career in MMA.

Hermansson made his MMA debut at East Coast Fight Factory: Impact on July 1, 2010. He defeated Chris Greig by third round KO. A 5-0 start helped Hermansson get signed to Bellator MMA. Hermansson's run through Bellator was somewhat forgettable, losing to Daniel Vizcaya by split decision (Bellator84) and Jason Butcher by triangle choke (Bellator 93). Hermansson would return to Europe, where he would compete in Cage Warriors, Warrior Fight Series, and Vennator FC. Hermansson would go 8-0 during this time with six finish victories, capturing the Cage Warriors Middleweight Championship against Norman Paraisy (Cage Warriors FC 69) via fourth round rear naked choke. He defended his Cage Warriors belt twice (Cage Warriors FC 71 and 75) and also claimed the WFS Middleweight Championship by defeating Karlos Vemola via armbar (Warrior Fight Series 4).

Hermansson made his UFC debut on September 3, 2016 at UFC Fight Night: Arlovski vs. Barnett. He defeated Scott Askham via unanimous decision. Judges were not necessary for ten of Hermansson's next eleven fights. He defeated Alex Nicholson (UFC Fight Night: Gustafsson vs. Teixeira), Brad Scott (UFC Fight Night: Pettis vs. Moreno), and Thales Leites via TKO (UFC 224), and he submitted Gerald Meershcaert (UFC on Fox: Lee vs. Iaquinta 2), David Branch (UFC on ESPN: Barboza vs. Gaethje), and Kelvin Gastelum (UFC Fight Night: Figueiredo vs. Benavidez 2). Hermansson was submitted by Cezar Ferreira (UFC Fight Night: Bader vs. Nogueira 2) and TKO'd by Thiago "Marreta" Santos (UFC Fight Night: Brunson vs. Machida) and Jared Cannonier (UFC Fight Night: Hermansson vs. Cannonier). The only decision during this run was a UD win over Jacare Souza as the main event of UFC Fight Night: Jacaré vs. Hermansson on April 27, 2019. 

Hermansson is 2-2 in his last four fights, with all four fights going to the judges. During this stretch, Hermansson defeated Edmen Shahbazyan (UFC Fight Night: Font vs. Garbrandt)  and Chris Curtis (UFC Fight Night: Blaydes vs. Aspinall) and lost to Marvin Vettori (UFC on ESPN: Hermansson vs. Vettori) and Sean Strickland (UFC Fight Night: Hermansson vs. Strickland). 2022 has been an up-and-down year for Hermansson. In the Strickland, fight Hermansson was unable to take Strickland to the ground and or to defend against Strickland's persistent and effective jab. Sal D'Amato strangely gave Hermansson a 48-47 despite being dominated throughout the fight, with Derek Cleary and Junichiro Kamijo giving Strickland 49-46 nods. Hermansson looked much better against Strickland's teammate in July, consistenly picking Curtis apart from the outside and having Curtis badly hurt up against the cage in the second round. Hermansson won via unanimous decision.